The cffrml_receive() function extracts a length field from the packet header and, when FCS is disabled, subtracts 2 from this length without validating that len >= 2. If an attacker sends a malicious packet with a length field of 0 or 1 to an interface with FCS disabled, the subtraction causes an integer underflow. This can lead to memory exhaustion and kernel instability, potential information disclosure if padding contains uninitialized kernel memory. Fix this by validating that len >= 2 before performing the subtraction. Reported-by: Yuhao Jiang <danisjiang@gmail.com> Reported-by: Junrui Luo <moonafterrain@outlook.com> Fixes: b482cd2053e3 ("net-caif: add CAIF core protocol stack") Signed-off-by: Junrui Luo <moonafterrain@outlook.com> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/SYBPR01MB7881511122BAFEA8212A1608AFA6A@SYBPR01MB7881.ausprd01.prod.outlook.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>